Process for the recovery of ammonium chloride from solution



Wfl

@ande/15er Filed May l2, 1930 June 13, 1933.

PROCESS FOR THE RECOVERY OF AMMOIUM CHLORIDE FROM SOLUTION Pump if??? Iau /an INVENTOR 'Ha/f Cole Ar'roRNEY Patented .lune 13, 71933UNITE'D'STATES j nay comi, or l oLvaY, Lnnwfonx, fassienon `To aansoifvnl rnocnss contrainte y on `1so'1."V`aY`,neuf xonmnponronnrron on;NEW YORK" n i PROESSFB rHsEQVERY-GF AMMOUMLORIDE FROM SOLTI'N" Appnetion`funi Mey 12; 193e. semi no. Listens.

i :i This invention relatesto `a process infor, the

`recpvery lof solid ammonium :chloride from Solutions.` \Moreparticularly,` thisfinvention relates to the recovery olfammoniumchloride f rfrom :solutions containing `ammonium `chloride togetherWithi sodium chloride, sucl'r as ftheilteiwliquor:lfronr theammonia-soda i `eprocess.;`

solution ofifsodium chloride. lwithfammonia .and carbon-idioxide;` Thereaction Vtaking l :carbonateuisprepared 4by the reaction ota i f Ixlacei` may "be" expressed; by` the following `The sodiumrbicarbonateprecipitates as i a i solid While the ammonium ,Chloride remains llilZli:formation of:sodiumlbicarbonate and am-` 'Linx solution. The :reaction:resulting in the monium Vchloride `doesnot, however,` go to completionso tliatlthe ammonium chloridei solution7 `after separationffrom the fprecipitated sodium bicarbonate,` contains ammonium carbonate and lsodium chloride together with minor proportions of any impurities iViiiovalof the sodium bicarbonate `for re-use i i in y the ammonia-sodagprocess. This recov- 4ery of'` ammoniamay be accomplished first by yheatiirg the filter `liquor oyrintroduction of steam ldirectlyinto the`liquor followed bya `treatmentof`the liqimr Withvlime and a second:heating-cto `drive out the remaining ain- `moniaj. Diumgthe iirstiofthetWo distilla tions .byineans of hea the so-calleolfffree-am-` i moniaccntentlisz evolved,` thatis to say, the

ammonia whichexists in tlieliquor as caus ticwan'in'ionia or `asammoniumu.:carbonate. l1 The `treatment' with lime n is tor the Vpurposeof: 1 conyertin the ammonium chloride` into caustic ammonia an d calciumchloride so that #upon the second distillation this `sofcalled linedammonia, i. e., the" ammonia presentiii Vthe liquor as ammonium chloriderprior to its aminonia-soda process, sodium bi- Witli such a process,the lilter liquoruis sub-f4 )cctecl to evaporationountil sodiumchloride`begins to crystallize out; Atthispointfthe evaporation" is stopped andthe concentrated liquor cooled by evaporation' of 1a' portioii'. of ithe `Water under :a reduced pressure `,to crystallize out ammoniumchloride. `'lliemotlier` liquor, after separation from the ammoniumchloride crystals, may again'wbe concentrated which `Will result i in"thezprecipitation of sodiunnchlorde andyas soon as ammoniumchlorideoybegns" to precipitate, the" sodium J t has also beenproposedto the `chloride isseparated from the Vhot solution and thesolution cooled to crystallize out additionalammonium chloride."VY/"liilethev 1 ammonium chloride" product obtained `bythe process b asdescribed is `satisactory i for some aises,4 it nevertheless@containsJmaterial `proportionsof sodium i chloride as an impurity whichronden the ammonium chloride `unsat- .iisactoryv for/many purposes.A Thetreat*G i ment"` of1 ammonium chlorideisodiumfi chlo- '1 ride liquorsinaccordance with sucli'a process, isparticularly disadvaiitageous whenthe ride for every one part of` ammonium chloride. i i N i Ti `Amodification of thisprocesshas also been `liquors contain an amountofsodium chloride i f which is in excessof one part of sodium Chloproposed in Which-the cooling ot` thelconceiitrated ammonium `chlorideliquorn `isiac- -tor example, by indirect heat interchange moniumchloride `is, however inefficient and .dfiflicult in :carrying outwT'heammonium chloride `crystallizesout upon the-:su'irfaces through whichthe exchangefof heat is taking placer and `thus inhibits the A"heattransfer.

Furtlierniore,V metal apparatus which is relquired for thus coolingthesolutionisattacked and rapidly destroyedby tlie'solutions undergoingcrystallization;y my

i libenationbylmeaiis oliine, ijs rec'zoi'ered. f: It is aiiuobjectofthis inventiontolrecover i complished by meansotherthanibyevaporatfing the solution under areduced pressure-as,

130 lion, a. solution solid ammonium chloride from aqueous solutions ofthis material together with sodium chloride in an economical mannerwhich gives an ammonium chloride pro-duct of relatively high purity. Itis a. :further object of this invention to provide a` processparticularly applicable for the treatment of aqueous solutions ofammonium chloride containing sodium lchloride in which there is not morethan about l part of sodium chloride to every l part of ammoniumchloride, wherebyn the cooling. of. concentrated ammonium .chloridesolutions containing sodium chloride may be accomplished by evaporationofthe solutions 'under reduced pressure without excessive contaminationofthe precipitated ammonium .chloriderwith sodium chloride. It is avfur- -ther 'object of thisIinvention to provide an i eflcient 1 process.for the treatmentV of filter 5520 liquor from the ammonia-soda processfor the :recovery therefrom of a-pure ammonium chloride whereby theammonia-soda process may beused as amethod for the conversion xofeammonia into ammonium-,chloride of satis- 'W5-factory ypurity and thesimultaneous product tionV of-sodium. bicarbonate. 'Other objects-fofmthe invention will be in part be obvious :.-and' will in partappear hereinafter.

In carrying-.out the process of this invencontaining .ammonium:.chlorideand sodium chloride is concentrated until-the solutionhas apredetermined degree y of .unsaturation with -respect to sodiumachloride. The thus concentrated solution is 935-cooled-bysubjecting itto a diminished pres- -sure'Whe1-el1pon Water is evaporated and the-temperature of the solution is lowered to a 1 pointat whichsolidammonium chloride precipitates out.l In vthe treatment of thefilter Fliquor-from .theammonia-soda process in ac- -cordance .withthisinveution, it is preferable tou first add tothe flterliquor asolution of ;calcium chloride whereby` .ammonium car- :.-bonateisconvertedin large part .into calcium l5-carbonateandammonium-chloride. After re- -movali vo-Lthe .calcium carbonateprecipitate, the thus treated filter liquor is placed under .a Areducedpressure and the .free ammonia --Iremaining in-the liquor' is recovered-there- `-rfrom by treating the-liquor with steam.l Fol- -lowingl theVremoval of the free ammonia contentof"y the liquor,`it isevaporatedtothe de- .;sired 'predetermined concentration with re- .spectLto.itssodium chloride content and cooledV tofpreciptate ammoniumchlorideV by further evaporation of water Linder a reduced zzpressure.'AThe first evaporation of the soluy.tion iszpreferably carriedout `underthe. same reduced Vpressure as isemployed for the re- V30.'moval. of.free ammoniaa'nd the steam generated by. this 'evaporation Vis employedVfor -thezliberation of..theff-ree ammonia from a -succeedingportion?o-ii' filter liquor.

The inventionfaccordingly comprises-the 'f-65 severalstepsandtherelationo` one or more of such steps with respect to each ofthe others thereof which will be exemplified in the process hereinafterdisclosed and the scope of the invention will be indicated in theclaims.

For a. fuller understanding of the nature yand objects of the invention,reference should -behad to the following detailed description taken inconnection with the accompanying drawing in which Fig. 1 is adiagrammatic representationof the' process of this invention as carriedout in .one type of apparatus forthe recovery of ammonium chloridefrom'filte'r liquor of the ammonia-soda. process, and

Fig. 2 is a phase rule diagram for two eX- .amples of filter f'liquorfrom" the ammonia- .soda process and. they conditions under which theVprocess lof this invention isoperated for the treatmentk of. suchliquors.

Il .Referring now to Fig.A 1,.the numeral l1 inldicates al carbonatorfor the' treatment of .'-filtenliquor from the ammonia-soda process,

which liquor is passed into the carbonator from apipe 2 with calciumchloride solution VIentering from a pipe 3.1TheamiXed-solutions Iare:treated Ywith aagas containing carrbon'dioXide passed-into thecarbonator from a -pipe 4 and the gas, after contactnwith the solution,is vented from the carbonator through a pipe 5. The carbon-dioxide gascombines with ammonia contained in' the'ilter liquor as caustic ammonia(NH3 or NH-40H) or as ammonium carbonate [(NHQ') 2G03] to 'v formv.ammonium bicarbonate. f. The.ammonium'bicarbonate reacts with Vthe.calcium :chloride to Vform ammonium .chloride y"and a precipitate .ofcalcium 4carbonate. :The rliquor containingv the suspended calciumcarbonate :passes through apipe 6 to affilter 7 where thecalciumcarbonate is vremovedfand the liquor .passed through a pipe 8 toaustorage vtank 9. vThe conversion or ammonia .and ammoniumcarbonateinto cal- ,cium `carbonateand .ammonium chloride. in -carbonator 1 isincomplete andthe liquorin storage tank 9 still contains free ammonia.

.@Fromastoragetank 9-the filter liquor is Hpassedzthrough apipe 10 into.the top of a closed vessel y11. The upper portion '12of vessel 11contains a .packing material `and serves-as a decomposer while a lowerportion 213 of vessely 11 serves asian evaporator. -The liquor from pipel0 issprayed rover-the ypacking-nin Adecomposer landrin passingdownwardlythrough :the packing iszintimately contacted with'steamevolved,.asy is later..descr.ibedin .evaporator 13.' .This .steampassesupwardly from the evaporator through .the-decomposerand serves to heat:the liquor landdistilllout of it the free am- .moniaw After treatmentin decomposer 12 the vliquorzpasses into'evaporator'l. Liquor fromtheevaporator. is continuously with- :drawnthrough apipelllliandiby meansof a pump 15'circulated'throughipipe 16, aheater 1r, and a pipe is, backte evaporator. 11a `In passin through heater 17 the liquor is heatedbyin irectxcontact .with steam `passed to y heater-17 throughapipe19ywThe liquor in "V evaporator 313 isithus maintained at a tem`about 19inchesof mercury, suflicientlyi loe-` lowl atmospheric pressureto cause the solu- 15 tion in evaporator 13 to be concentrated and togive off steam whichthen passes throughV decomposer l2yand serves,asuoted, for the liberation of `free ammonia from. the .liquor passing.`therethrough.` The ammoniacal zo gases :evacuatedwfrom vessel llthroughpipe 23 pass into a condenser 22 which is provided with? packingmaterial. In` the condenser thegases are directly contacted'with conden`,sate which forms from` these ammoniacal 25 gases `upon their beingcooled. The `condensate is circulated through pipes24, 25 and 26 andcooling coil 27 by meansof a `pump 28 fromtthebottom of condenser 22.`The thus circulated and cooled condensate 3o" returns to the top ofcondenser 22 where itis sprayed over `the packing therein and in `its idescentkthrough the condenser `serves to cool the; ammoniacal ,gasespassing therethrough and condense an ammonlacal solut1on,`pr1n` "85cipally consisting of Water7 from these gases.

The amount of condensate `thus reeirculated through condenser 22 ismaintained substan-l tially constant bywithdrawing a portion of thecondensate through a pipe 29 which com-I"` municates with pipe 25.Theresidual gases froml which the condensible portionshave beenseparated are removedifrom contact with the condensatein condenser 22 bytheoperation ofvacuum pump 20.`

In evaporator l1 the filter liquor `is concentrated andwhile "thesolution still has a" predetermined `degree `of unsaturation withrespect tosodiumchloride, liquor is continuously withdrawn` from the`evaporator through a'pipe 30 andpassedto a "tank 31. The` rate ofWithdrawal `of solution `from evaporator 13 *and admissionof solutiontovesselll'irom pipe 10 are so regulated that the composition ofthesolution in evaporator spect `to its concentration of sodium chloride.`From `tank31`the .hot concentratedffilter liquor passes through axpipe32 into a cryishedlpressure.` and is cooled by evaporation of `Waterfrom the solution to a temperature at which solid ammonium chlorideisformed. The `diminished pressure in crystallizer 33 is maintainedbymeansof a vacuum pump `34 and a condenser 35which communicates withliquor i undergoing 13 remains substantially Constant with readstallizer 33 `Where it issubjected to a diminthetop` of crystallizer 33by waywofpipes-33i and37. `The Water `in the gas evacuatedfromcrystallizerl33 `is condensed in condenser 35 and the residual gasdischarged bymeansof vacuum pump 34 through fa pipe 33; The liquor fromtank 31 is preferably introduced below the surface of thevliquor incrys'tallizer` 33. By introducing the hot solution intoa body of cooledsolution in .the crys't-allizer,` the physical qualities ofthe crystalsformed are improved.` The crystallizerlmay also bei" `equipped with astirrer for facilitating lthe crystallization. i From 'crystallizer 33the "cooled liquor containing solidf ammonium chloride and sodiumjchloride in solution passes through a pipe 39 to a seal tank 40.` A`

portion of the liquor from seal tank 40 con` taining suspended `solidammonium chloride is returned to mingle with the liquor in tank 31 byway ofa pipe 41`and `thus facilitatesthe`` formation `from i the liquorof ammonium` chloride crystals of audesi'red character. This" cooledliquid returned totank 3l lowers the temperature of the concentratedliquor from plpe 30 and the crystals of ammonium 'chlo- .ridev carriedwith itformj nuclei upon which1 new crystalsmay form rom'theconcentrat-i ed solution.- It hasbeen `found that when an amount ofcooled solution is returned-to tank 31such thatthe liquor fromevaporator 13 having a temperature of about 300 (his cooled `in tank` 31to about 50c C., and the thus cooledjand seeded liquor is further cooledin flash crystallizer" 33,V an ammonium chlo`4 ride product having acommercially suitable particle size isobtained. y The otherportion i ofthevsuspension of ammonium chloride is,`` however, passed through a pipe42 to aiilter 43` where thesolid ammonium chloride is `separated from"the `mother liquor. "This mother liquorleavesfilter 43 througha pipe andis preferably returned to the am#` monia-sodaprocess `for recovery oftheresid*` ualammonia content ofthe solutionby treatmentwith limeandfdistillation of the thus liberated ammonia. Thefammonia thus 'ref`coveredftogether with the ammonia in the ammoniacal gases dischargedfrom vacuum` pump 20, serves inthe `ammonia-sofla process. for theproduction of additional quantities of sodium bicarbonate and the filterliquor is treated as above described for lthe recovery of the ammoniumchloride simultaneously `produced. l The ammonium chloride separated`from" the `mother liquor filter 43 may be` subjected while in the`filter to washingwith water to free itfrom adhering mother `liquor andthe resultant wash water added to the mother liquor `which isremovedthrough pipe 44. The ammonium chloride is withdrawn from the filter andmay be passed to a dryer i and then packed .for` shipment or employed iin any desired manner.`

Referring now to "Flgx 2 this figure shows i the conditions of operationin evaporator 13l and crystallizer 33 in practicingy this .invention. Inthis figure the lineA-B represents the concentration of a filter liquorfrom the ammonia-soda process atV which it is in equilibrium Withsolidsodium .chloride and solid ammonium chloride at varyingtemperatures. For example, point C represents the composition of such asolution ata temperature of 90 0 C. and point C1 represents thecomposition of such a solution at a temperature of 30 C.

Lines C-D and C-D represent the compositions of filter liquor inequilibrium with solid amlnonium chloride at the indicated temperaturesof 90O C. and 30 C. respectively, and lines C-E andv C--E similarlyindicate the compositions of filter liquor in equilibrium With solidsodium chloride at ther 0 ammonium chloride and 17.5 parts ofsodifurther cooled in crystallizer 33 by evaporation of water therefromto a temperature of about 30 C. As a result of the loss of Water fromthe solution, the proportion of sodium chloride 'to Water increases toabout22 parts of sodium chloride to100 parts of ivater and solidammonium chloride is Vprecipitated from the cooled solution so that themother liquor, in addition to, this sodium chloride, contains about 27parts of ammonium chloride for every 100 parts of ivater. The pointsindicated by F, G, H and I in Fig. 2, represent respectively thecomposition of the filter liquor prior to its concentration, thecomposition of the concentrated liquor, the composition after beingcooled to 50 C. by return liquor and the composition', of the motherliquor from yWhich solid am-` monium chloride has precipitated. The lineF'-G represents theV change in composition of the liquor duringconcentration, andthe line G-H-I represents Athe. change in compositionof the liquor during its cooling.

n As noted above, the concentration of the still has a predetermineddegree of unsaturation With respect to sodium chloride. The line J-Jrepresents the composition of a r .filter liquor which, for anyfgiventempera- J 'ture when placedl in contact with solid soditor 13 until itcontains about 50.3 parts of` mixing with cold liquor from crystallizery33' to a temperature ofrabout 50 C. andis then filter liquor isinterrupted While the solution-y um ch'loride,will dissolve' about 2Vparts of ride in the proportions representedby` any point in the area ofFig. .2 below theline J-J. is a solution having ar predetermineddegreefof unsaturation With respect to :sodium .chloride as this `termis employed in'this specification and in the claims. It has been .1

found that by `thus limiting the degree of concentration of an ammoniumchloridesodium chloride` solution that the thus concentrated solutionmay be cooled byevaporation of Water therefrom to a temperature at whichsolid ammonium chloride precipitates and the ammonium chloride may berecovered and after being freed from the mother liquor, is in asubstantially pure state.

-Itj may be advisable, in certain instances, to supplement the coolingdue to evaporation ofWat-er from the solution under diminished npressure with a cooling of the solution by meansfof indirect heattransfer to a cooling medium or this supplemental cooling mayA resultfrom an incidental loss of heat from the hot solution to the surroundingatmosphere during the conveyance of the solution from Vthe evaporator tothe crystallizer. For example,l if a solution represented by point K ofFig. 2, containing 20 parts of ammonium chloride and 5 parts of sodiumchloride for every 100. parts of Water, is concentratedl at atmosphericpressure until it has la composition represented by point L, it may bedesirable to cool the solution to a temperature of-abiout, for example85 C., Without evaporation ofwater, during which cooling a part of theammonium chloride will pre-1 cipitatevout, and then subject the liquorto cooling by evaporation of water therefromV under a diminishedpressure, as for example to a temperature of about 30 C. The linev K-Lof Fig. 2 represents the composition of the solution thus treated duringits concentration and the line L--N-M represents the composition of thesolution during the cooling to precipitateout ammonium chloride.l

On the other hand, the solution may be simultaneously cooled both byloss of heatl to a cooling medium and 'by evaporation under a diminishedpressure, inwhich case the line` L-M may vrepresent the composition .ofthe solution under such aco'oling.` It has been found, however, that in(all cases in the cooling-.of the concentrated lliquorfthe amount ofwater 'evaporated from the'liquor during such cooling should becoordinated with the degree of unsaturation of the yconcentrated liquorwith respect to sodium chloride so that throughout vthe cooling, theliquorv remains unsaturated with respect to the sodi- A um chloride. f

Sincev certain changes may be made'inv carrying out the'above processWithoutde` edito `refer to a Dsolidaunmoniumchloridelis formed.`

` parting frornthe scope of the invention, it ,i

is "intended that all matter contained inthe above description shall beinterpretedas il- Y n lustrative` and not in allimiting sense. 1 `lllhenf5) `1n the speclfication` and claims "reference is m solution stillhasa4 predetermined degreei of unsaturation with respect to sodiumchloride,` and cooling 1 the i `concentrated l l solution by evaporationrofl` Water therefromA` under 'a `din minished pressure to a temperatureat which y 2; iThe process "of recovering ammonium y chloride from r anaqueous solution containing ltheisame; together with sodium chloride, ly inan amount notgreaterthanl about one part of sodium chloridejforevery lone part of am-` monium chloride; fwhich comprises concen-`tratingsaidlsolutiom` interruptin 11 thereoncentrationf`vvhilethcsolution still as a pre- 1detcrmined degree of unsaturationwith rei spectto sodium chloride, and cooling the con-` centratedsolution by evaporation of i water therefromunder a diminished pressuretoa temperature at which solid ammonium chloridelisformed'. i v

i 3. l'lihel process of recovering ammoniumV chloride fromanaqueous'solution containing y the same,j-together With "sodiumchloride,

Whichcmprises concentrating said solution,

` `interriipting the concentration while the i 'l' solution still has apredetermined degree of unsaturation with" respectfto sodium chloride,i? cooling j the i `concentrated solution by evaporation lof Twatertherefrom under a di- ,o minished pressure'to a temperatureat Whichsolidammonium" chloride is formed,` and co-` ordinating the" degree`of"`unsaturation ofsaid y solution and the amountof Waterevaporated `1therefrom during said cooling whereby thel solution `throughout thecooling remains una* saturated with respect to sodium chloride.

4. The process of recovering ammonium chloride from anraqueous solutionvcontaining the same,-togeth`er `vvith sodium chloride,`

which comprises concentrating said solution,

im interrupting the i concentration While the` solution still has apredetermineddegree uof. unsaturation with `respect to sodium chloride,introducing into the l`concentrated solution a suspension of solidlammonium" `chloride 'in a m solution of ammonium "chloride, and coolingn thethustreated solution by evaporation of` water therefrom under adiminished pressure `to atemperature at which solidammo- Vniu'm chlorideis formed; y J W 15. Thefprocess'of `recovering arlllruonium` chloride`from the filter liquor ofthe ammonia-soda process containing the same,to-

gether` with sodium chloride, which cornprises concentrating said filterliquor,interrupting the concentration while said; liquor still has apredetermined degree of unsatura-y tion "with lrespectto sodiumchloride, and

cooling the concentrated liquor by evapora- 1` f tion of water therefromunder a diminished pressure to a temperature at which solidam-i` moniumchloride is formed; i 1 y g'lhe process lof recovering ammonium chloridefromv the filter liquorof the-am monia-soda process containing the same,`together lvvithf` sodium chloride, which colm-` prlses concentratlngsaid filterliquor, inter rupting the concentrationwhile said liquor istill has a predetermined degree of unsaturation with respect to sodiumchloride, cooling the concentrated liquor by evaporation of watertherefrom under a diminished pressure to 'a temperature atWhich solidammo- 1 nium chloride isvformed,and coordinating* theldegreeofunsaturationof said liquor and the `amount of Water evaporated therefromf during said cooling whereby `thetfliquor y throughout thecoolingremains unsaturate with" respect to sodium chloride: j; i

`7. The processwof recoveringanlmonium chloride frointhe `flterliquor ofthe ammomia-soda process containing the same,` together With sodiumchloride, Which comprisesconcentrating said filter liquor, interruptingthe concentration when said liquor contains an amount` of ammonium"chloride corresponding tosaturation at about C., coollng-.theconcentrated liquorto` about 30"` C,l saidwcooling including a coolingbycvaporationof:.vvater `therefrom under a diminished pressure, andseparating solid ammonium Chloride thus Pmduced from `the `mother lq-`uor. i f i i s los `8.w'.l`he process of `liberating free ammonia i froma liquor containing the same, which comprlses subjecting said liquorto areduced pressure,and While i under said reduced pressure, driving .outofi thelliquorits free ammonia` content by treatment with steam, heatingthe thusltreatedliquorto evaporate steam therefrom, and employing thefsteamthus obtained for the liberation of "free ammonia 1n thefmannerdescribedfromfa succeeding` portion of said liquor. i

9. The process of liberatingfree ammonia from the :filter liquor oftheammonia-soda process, `Which comprises subjecting said filterliquorto a` reduced pressure, and while under said reduced pressure, drivingout of the liquoriits free 'ammonia content `by the treatment withsteam, heating the thus treated liquor to evaporate steam therefrom, andemploying the steam thus obtained for the liberation of freeammoniay inthemanner described from a succeedingportion Vof said filter liquor. i

l0: In'a'processfor thefrecovery of conf densible vapor froina body ofmaterial .under areduced-pressure, said vapor forming a liquidcondensate, vthat improvementwhich comprises placing said body in aclosed vessel, continuously evacuatingl gas and vapor from said vessel,condensing said vapor While v undera. reduced pressure by direct contactWith a cooled body of condensate of said vapor and removing theuncondensed evacu- Y ated gas from contact with' said condensate. 1l.:Ina process of liberating free ammoniay from the'filter liquor of theammoniaseda process, that" improvement which comlprises subjecting saidliquor to treatment Withsteam infa closed vessel, continuouslyevacuating a gaseous mixture of Water vapor'y and gas from said vessel,thereby maintaining a'reduced pressure Within the vessel,`

condensing a portion ofsaid gaseous mixture, Whilemunder` 'a reducedpressure, by directfcontact therewith of a cooled body of condensateofsaid mixture and removing the uncondensedevacuated gas yfrom contactwith said condensate. v

`12.]The process rof recovering ammonium' chloride from thefilter liquorof the ammonia-soda processiwhi'ch comprises subjecting said filterliquorto reduced pressure and While under said reduced pressure drivingoutvof the liquor its free ammonia contentby treatment With steam,heating'the thus treat-`r ed liquor to-evaporate steam therefrom yandconcentrate thevliquor, employing the steam* thus obtainedforthelliberation of free am' monia in the manner described fromVa-succeeding. portion `of said iilter liquor, interrupting theconcentration Whileth'e liquor still-has* a predeterminedfdegreeofunsaturation with respect to sodium chloride,-and

cooling the `concentrated -liquor by evapora-- tion of Water therefromunder a diminished pressure to a temperature at Which'solidammoniumchloride is formed:

` 13; The process of recovering yammonium chloride from the filterliquor of theammonia-soda process Which comprises subjecting said filterliquor to a reduced pressure and While under said reducedpressuredriving Y out of the liquor its freel ammonia'content by treatment withsteam, heating the thus treated liquor to evaporate steam therefromv andconcentrate the liquor, employing the steam thus obtained fortheliberation of free ammoniafin the manner described from a succeedingportion of said-lter liquor, interrupting the concentration Whiletheliquor still has a predetermined degree' of unsaturation Withirespectto sodium chloride, and coordinating'the degree of unsaturation of saidliquor-and the amount of Water evaporated-therefrom during saidcooling', Whereby the liquor throughout the cooling remains unsaturatedwith respect to sodium chloride.

14. The process of recovering ammoniuln chloride'from the iilter'liquorof the ammonia-soda process which comprisesadding c alcium chloride .tosaid liquor, removing Aprecipitated-calcium carbonate, subjecting thethus-treated filter liquor to a reduced pressure, and While under saidreduced pressure,

driving out of the'liquor its free ammonia content by treatment Withsteam and heating the thus treated liquor to evaporate'steam therefromandconcentrate theliquor, employing the steam'thusiobtained for theliberaLv tion'offree annnonia vinthe manner described from -a succeeding:portion of said filter liquor, interrupting the concentration when saidliquor contains 'an amount of'ammonium chloride-correspondingto-saturation at about 70 C., cooling the concentrated liquor byevaporation of Water-therefrom lunder a diminished'pressure to atemperature. of about 30 C., and separatingsolid ammonium chloride thuslproduced fromthe mother liquor.

15. The process of recoveringfammonium chloridey from the filter liquorofv the ammonia-soda process which comprises adding calcium V,chlorideytov said liquor,vtreating the liquor wvith'tlie fadded vcalcium chloride`With'4 carbon dioxide, removing Aprecipitated cal-- cium carbonate,subjecting the thustreatediilterliquor to a reduced pressure, and .Whilef under said reduced pressure, driving out-vof! the liquorits:freeammonia Vcontent by treatment With steam and heating the thustreated liquor to evaporate-steam therefrom and concentrate the liquor,employing the steam thusV obtained for vtheiliberationpof free ammoniain the manner described from asue-` ceeding portion of saidfilter-liquor, inter-Yv rupting the concentration when Isaid liquorcontainsran amount'of amlnonium chloride corresponding to saturation atabout 70 C., introducing-into the'concentrated solutlon a suspension ofsolid ammonium.l chloride-in;

a solution ofzammonium chloride having a temperature of about SOQ-C. orbelow and in Y amountA suiiicient tol cool the said concentratedsolution to about c C., cooling the -thus treated liquor by evaporationof Water therefromunder a diminished pressure to a temperature of aboutv30 C., and separating solid amonium chloride thus produced from' themother liquor.V

` 16. The processv of recovering ammonium chloride from an aqueoussolution containing the same together with sodium chlorider i SO .liquor with steam to liberate its free ammoniuin chloride from filterliquor of the ammonia-soda process, that improvement Whichconiprisesadding calcium chloride tov said liquor, subjecting the liquor With theadded calcium chloride to treatment with carbon dioxide, and removingfrom the thus treated liquor precipitated calcium carbonate.

19. The process of liberating free ammoniafrom the filter liquor of theammonia-soda process Which comprises subjecting said filter liquor to areduced pressure, and While uni der said reduced pressure, driving outof the liquor its free ammonia content by treatment with steam, heatingthe thus treated liquor under a reduced pressure substantially the saineas the aforesaid reduced pressure to evaporate steam therefrom, andemploying the steam thus obtained fortlie liberation of tree ammoniainthe manner described from a succeeding portion of said filter liquor.`

`S20. In the process of crystallizing ammonium chloride from a solutioncontaining the sameby cooling said solution by evaporation of Watertherefrom under a diminished pressure that improvement which comprisesintroducing into the solution to be cooled solid `particles of ammoniumchloride.

2l. In the process of crystallizing ammonium chloride from a solutioncontaining the same by cooling said solution by evaporation of Watertherefrom under al diminished pressure that improvement which comprisesintroducing into the solution to be cooled a suspension of solidammonium chloride in a solution of ammonium chloride.

2Q. The process of crystallizing ammonium chloride from a solutioncontaining the saine which comprises mixing therewith a suspension ofsolid ammonium chloride, cooling the mixture by evaporation of Watertherefrom under a diminished pressure to a temperature at which solidammonium chloride is formed from the solution, and employing a portionof the thus cooled mixture as the suspension of solid ammonium chlorideused in the treatment of a succeeding portion of ammonium chloridesolution in the manner hereinbefore described.

23. The process of recovering ammonium chloride from an aqueous solutioncontain- `ing the same, together With sodium chloride,

`which comprises concentrating said solution, interrupting theconcentration while the solution still has a predetermined degree ofunsaturation Wth respect to sodium chloride,

and cooling the concentrated solution to a temperatureat which solidammonium chloride is formed.

24. In the process of crystallizing a material from a solutioncontaining the same wherein said solution is heated to concentrate itand the heated concentrated solution is cooled by evaporation of liquidtherefom un der a diminished pressure to form a suspension of saidmaterial in a mother liquor, that improvement which comprisesintroducing into the solution to be cooled mother liquor containing saidmaterial in suspension obtained by the aforesaid cooling of the heatedconcentrated solution.

`In testimony whereof I have hereunto affixed my signature.

RAY COLE.

